3D-printing (also known as 3D-rapid prototyping or additive material manufacturing) is a new manufacturing technology raised from the late 1980s. It is a kind of new digital molding technology. Three-dimensional objects may be produced rapidly by analysing some data such as computer aided design (CAD) model or computed tomography (CT) data and using accurate 3D-deposition under the control of computer. These objects can be of almost any shape or geometry, and are applied in many technical fields.
3D-printing is a revolutionary manufacturing technique based on the technical principle of printers and then manufactures layer by layer. It can be referred as ‘Additional material manufacturing technology’ while the traditional productive technique is referred as ‘Reductive material manufacturing technology’. It's featured as cost-effective, personalized and with short production cycles. The components produced by 3D-printing for airplanes, space shuffles and fusion projects are lighter, firmer and cheaper compared with regular ones, even without any waste. Thus 3D-printing has been renowned as “the most remarkable tool for the 3rd industrial revolution”.
In recent years, much attention is paid to research and develop 3D-printing to produce biomedical polymer material. The advantage of 3D-printing is that products can be designed according to each patient's specific condition with flexible design. In medical and health industry, personalized biomedical polymer material suitable for each patient is produced rapidly and accurately by 3D-printing. Meanwhile, the micro structure of the material is also controlled precisely. Therefore, the new technique of producing medical polymer material is undoubtedly promising when applying to biomedicine.
Coronary artery disease has endangered people's life in modern society, is one of common cardiovascular diseases. It's featured with high rate of prevalence, mortality, readmission and complications. For treating cardiovascular diseases, the treatment of coronary artery diseases is very important, and coronary intervention has become the primary method to treat coronary artery disease. So far, the development of coronary intervention involves 3 stages: percutenous transluminal coronary angioplasty, implanting bare-metal stents and implanting drug-eluting stents. Although the metal composition of stent body, polymer carrier and antiproliferative drug are improved a lot, two dilemmas remain unsolved: the metal material of stent and its cylindrical structure. The problems are as follows:
(1) The permanent existence of metallic stents could bring complications like late in-stent thrombosis, chronic inflammation, restenosis and stent fracture. Meanwhile, patients have to take lifelong anti-platelet drugs which would increase bleeding risk. (2) The diameter of coronary artery is gradually smaller and sometimes the gap of diameters between proximal and distal segments of culprit arteries could be remarkable which make the lumen of vessels sharply tapered. These days, traditional cylindrical stents are cylinder, may not suitable to these cone-shaped arteries with neither single stent nor two stents techniques: when implanting one stent may not expand efficiently caused by mismatch of stent diameter and vessel diameter thus lead to in-stent thrombosis, incomplete stent apposition, coronary dissection or in-stent restenosis. When implanting two stents, on the other hand, could increase the risk of restenosis and thrombosis due to overlapping area between stents, the total expense is raised. Additionally, traditional cylindrical stent couldn't match the hetero-morphic coronary artery such as aneurysm.
Aimed at above problems caused by metal material of stent body, the emergence of biodegradable stents emerged and marked the 4th revolution of coronary intervention. With regard to the conical/abnormal coronary artery, Biodegradable coronary stents suitable for the morphological characteristics of each patient are approved to have enormous Scientific, Economic and Social values.
Chinese patent CN104224412A discloses a method for producing coronary artery stent with 3D printing technology. By controlling 3D printing program, the mixture of stainless steel powder or nickel titanium powder with stearic acid powder are combined with adhesive to form the stent prototype, then after degreasing, sintering and cooling, eventually the coronary artery stent is generated. It uses metallic materials with 3D-printing technology to produce cylindrical stent, but it did not take the advantage of 3D-printing in customization, and not used the most advanced biodegradable materials, so it is failed to solve the problem of conical/abnormal vessel stenosis and failed to avoid the disadvantage of conventional stent. Unfortunately, it did not show great value in clinical practice.